This invention relates generally to data processing systems, and more particularly to a processor for use in an input/output processing system.
In the prior art, large multi-dimensional, multi-processor data processing systems utilize input/output processing systems for interfacing peripheral devices and the main processing unit. Such input/output systems are required for establishing data rate compatibility, addressing, and general data exchange control.
In the Honeywell 6000 Series large computer systems, for example, peripheral devices are connected to and controlled by microprogrammed peripheral controllers (MPC) which, in turn, are connected to the main processing units through input/output multiplexers (IOM).
The IOM is the coordinator of all input/output operations between the complement of peripheral subsystems and the main processor unit controller. The IOM operates essentially as a hard wired program device controlled by, and sharing memory with, a main processor. Data transfers between a peripheral device and main memory are accomplished by the IOM while the processor runs the jobs. The IOM includes a plurality of data channels for communicating with peripheral devices and a central channel which controls access to main storage for each of the data channels. The data channels include common peripheral interface (CPI) channels having a transfer rate in excess of 650,000 characters per second, which interfaces with many lower speed peripheral devices. Additionally, peripheral subsystem interface (PSI) channels have a transfer rate up to 1.3 million characters per second and are used with higher speed peripheral devices such as disks. Further, a direct channel is provided for front-end communication processors and allows data transfers as high as 1 million bytes per second.
External to the IOM and controlling the various peripheral devices are the MPC's for a plurality of high-speed disk devices, magnetic tape controllers, and unit record controllers for low-speed devices such as card readers and printers.